Proteomic analysis of Fasciola gigantica excretory and secretory products (FgESPs) interacting with buffalo serum of different infection periods by shotgun LC-MS/MS

Qualitative analysis of Fasciola gigantica excretory and secretory products coimmunoprecipitated with buffalo secondary infection sera shows dissimilar components from primary infection sera

Buffaloes cannot mount a robust adaptive immune response to secondary infection by Fasciola gigantica. Even if excretory and secretory products (ESPs) exhibit potent immunoregulatory effects during primary infection, research on ESPs in secondary infection is lacking, even though the ESP components that are excreted/secreted during secondary infection are unknown. Therefore, qualitative analysis of ESP during secondary infection was performed and compared with that of primary infection to deepen the recognition of secondary infection and facilitate immunoregulatory molecules screening. Buffaloes were divided into three groups: A (n = 3, noninfected), B (n = 3, primary infection) and C (n = 3, secondary infection). Buffaloes in the primary (0 weeks post infection; wpi) and secondary (-4 and 0 wpi) infection groups were infected with 250 metacercariae by oral administration. Then, sera were collected from groups at different wpi, and interacting proteins were precipitated by coimmunoprecipitation (Co-IP), qualitatively analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and annotated by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses to infer their potential functions. In group C, 324 proteins were identified, of which 76 proteins were consistently identified across 7 time points (1, 3, 6, 8, 10, 13, and 16 wpi). Compared with 87 proteins consistently identified in group B, 22 proteins were identified in group C. Meanwhile, 34 proteins were only identified in group C compared to 200 proteins identified in group B. Protein pathway analysis indicated that these proteins were mainly involved in the cellular processes and metabolism of F. gigantica. Among them, 14-3-3θ was consistently identified in group C and may be involved in various cellular processes and innate immune signalling pathways. Members of the HSP family were identified in both groups B and C and may function in both primary and secondary infection processes. The proteins discovered in the present study will help to deepen the understanding of the molecular interactions between F. gigantica and buffalo during secondary infection and facilitate the identification of new potential immunoregulatory molecules.

Immune modulation of goat monocytes by Fasciola gigantica Legumain-1 protein (Fg-LGMN-1)

Legumains belonging to C_13 peptidase family of proteins, and are ubiquitously disseminated among all vertebrate and invertebrate organisms, and have been implicated in innumerable biological and cellular functionality. Herein, we characterized and evaluated immunoregulatory characteristics of Legumain-1 from Fasciola gigantica (Fg-LGMN-1) during its interaction with host immune cells. The isopropyl-ß-d-thiogalactopyranoside (IPTG) stimulated RFg-LGMN-1 protein was positively detected by rat serum containing anti-RFg-LGMN-1 polyclonal antibodies. Furthermore, the uptake of RFg-LGMN-1 by goat monocytes was successfully confirmed using Immunofluorescence Assay (IFA). The immunohistochemical analysis revealed the native localization of LGMN-1 protein on the periphery and internal structures such as suckers, pharynx, and genital pore of the adult parasite, thereby validating its presence in excretory-secretory (ES) products of F. gigantica. The RFg-LGMN-1 co-incubated with concanavalin-A (Con-A) stimulated the increase of interleukin 2 (IL-2), IL-10, and IL-17 in monocytes derived from peripheral blood mononuclear cells (PBMCs) in the concentration-dependent manner. However, the IL-4 cytokine in response to the RFg-LGMN-1 protein declined. These results illuminated the role of LGMN-1 during the parasite-host interface. Our findings elaborated additional evidence that Legumain protein play a role in the manipulating host immune responses during parasite infections. However, further evaluation of RFg-LGMN-1 protein in context of its immunomodulatory roles should be conducted to enhance our understandings of the mechanisms employed by F. gigantica to evade host immune responses.

Development of a novel method for diagnosis of fasciolosis based on cathepsin L7 in ruminants

Fasciolosis is a widely distributed zoonosis reported over 81 countries around the world. Good and early diagnostic method is critical in controlling this disease and prevention of injury to the liver and bile ducts. In this study, we identified a novel member (cathepsin L7) of cathepsin family from Fasciola spp.. Firstly, the biological character of CL7 was analyzed according to the information of cathepsin L family, and then rCL7 was expressed and purified, a new iELISA based on CL7 was developed. The results exhibited CL7 iELISA had 100% sensitivity 100% specificity in sheep (cut-off 1.329) and 100% sensitivity 93.75% specificity in cattle (cut-off 0.756). Moreover, anti-Fasciola CL7 antibodies could be detected in early Fasciola gigantica infected buffaloes, as early as 3 week-post-infection (WPI). In conclusion, it is suggested that CL7 with low cost, early detection, good specificity and sensitivity could be used as a candidate antigen for detection of ruminant fasciolosis.

Proteomic analysis of exosome-like vesicles from Fasciola gigantica adult worm provides support for new vaccine targets against fascioliasis

BACKGROUND

Extracellular vesicles (EVs) released by helminths play an important role in parasite-host communication. However, little is known about the characteristics and contents of the EVs of Fasciola gigantica, a parasitic flatworm that causes tropical fascioliasis. A better understanding of EVs released by F. gigantica will help elucidate the mechanism of F. gigantica-host interaction and facilitate the search for new vaccine candidates for the control and treatment of fascioliasis.

METHODS

Two different populations of EVs (15k EVs and 100k EVs) were purified from adult F. gigantica culture media by ultracentrifugation. The morphology and size of the purified EVs were determined by transmission electron microscopy (TEM) and by the Zetasizer Nano ZSP high performance particle characterization system. With the aim of identifying diagnostic markers or potential vaccine candidates, proteins within the isolated 100k EVs were analyzed using mass spectrometry-based proteomics (LC-MS/MS). Mice were then vaccinated with excretory/secretory products (ESPs; depleted of EVs), 15k EVs, 100k EVs and recombinant F. gigantica heat shock protein 70 (rFg-HSP70) combined with alum adjuvant followed by challenge infection with F. gigantica metacercariae. Fluke recovery and antibody levels were used as measures of vaccine protection.

RESULTS

TEM analysis and nanoparticle tracking analysis indicated the successful isolation of two subpopulations of EVs (15k EVs and 100k EVs) from adult F. gigantica culture supernatants using differential centrifugation. A total of 755 proteins were identified in the 100k EVs. Exosome biogenesis or vesicle trafficking proteins, ESCRT (endosomal sorting complex required for transport) pathway proteins and exosome markers, heat shock proteins and 14-3-3 proteins were identified in the 100k EVs. These results indicate that the isolated 100k EVs were exosome-like vesicles. The functions of the identified proteins may be associated with immune regulation, immune evasion and virulence. Mice immunized with F. gigantica ESPs, 15k EVs, 100k EVs and rFg-HSP70 exhibited a reduction in fluke burden of 67.90%, 60.38%, 37.73% and 56.6%, respectively, compared with the adjuvant control group. The vaccination of mice with F. gigantica 100k EVs, 15k EVs, ESP and rFg-HSP70 induced significant production of specific immunoglobulins in sera, namely IgG, IgG1 and IgG2a.

CONCLUSION

The results of this study suggest that proteins within the exosome-like vesicles of F. gigantica have immunomodulatory, immune evasion and virulence functions. This knowledge may lead to new strategies for immunotherapy, vaccination and the diagnosis of fascioliasis.

Proteomic analysis of Fasciola gigantica excretory and secretory products (FgESPs) co-immunoprecipitated using a time course of infected buffalo sera

Introduction

Widespread Fasciola gigantica infection in buffaloes has caused great economic losses in buffalo farming. Studies on F. gigantica excretory and secretory products (FgESP) have highlighted their importance in F. gigantica parasitism and their potential in vaccine development. Identifying FgESP components involved in F. gigantica-buffalo interactions during different periods is important for developing effective strategies against fasciolosis.

Methods

Buffaloes were assigned to non-infection (n = 3, as control group) and infection (n = 3) groups. The infection group was orally administrated 250 metacercariae. Sera were collected at 3, 10, and 16 weeks post-infection (wpi) for the non-infection group and at 0 (pre-infection), 1, 3, 6, 8, 10, 13, and 16 wpi for the infection group. FgESP components interacting with sera from the non-infection and infection groups assay were pulled down by co-IP and identified using LC-MS/MS. Interacting FgESP components in infection group were subjected to Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathway and gene ontology (GO) functional annotation to infer their potential functions.

Results and discussion

Proteins of FgESP components identified in the non-infection group at 3, 10, and 16 wpi accounted for 80.5%, 84.3%, and 82.1% of all proteins identified in these three time points, respectively, indicating surroundings did not affect buffalo immune response during maintenance. Four hundred and ninety proteins were identified in the infection group, of which 87 were consistently identified at 7 time points. Following GO analysis showed that most of these 87 proteins were in biological processes, while KEGG analysis showed they mainly functioned in metabolism and cellular processing, some of which were thought to functions throughout the infection process. The numbers of specific interactors identified for each week were 1 (n = 12), 3 (n = 5), 6 (n = 8), 8 (n = 15), 10 (n = 23), 13 (n = 22), and 16 (n = 14) wpi, some of which were thought to functions in specific infection process. This study screened the antigenic targets in FgESP during a dense time course over a long period. These findings may enhance the understanding of molecular F. gigantica-buffalo interactions and help identify new potential vaccine and drug target candidates.

Localization of the proteinase inhibitor activity in the fish cestode Eubothrium rugosum

The mechanisms enabling fish tapeworms to avoid proteolytic attacks by digestive enzymes of their fish host have been studied in less detail compared with mammalian cestodes. This study aimed to assess the inhibitory ability towards trypsin and chymotrypsin in Eubothrium rugosum, an intestinal parasite of burbot Lota lota, and establish its localization in the tapeworm. To this end, the worms were treated with Triton X-100 followed by differential centrifugation to isolate the tegumental brush border membrane. The protease inhibitory abilities of the worms were mostly determined by their excretory/secretory products released into the incubation medium. These inhibitory abilities proved to be linked mainly with the brush border fractions. Notably, the per cent inhibition of both studied digestive enzymes (trypsin and chymotrypsin) hardly depended on the duration of the parasite exposure in the incubation medium, probably due to intermittent glycocalyx renewal. Improved knowledge on functions of the excretory/secretory proteins produced by fish tapeworms may contribute to a better understanding of host-parasite relations and development of new approaches to the treatment and prevention of diseases caused by pathogenic helminths.

In silico characterisation of the complete Ly6 protein family in Fasciola gigantica supported through transcriptomics of the newly-excysted juveniles

Fasciola gigantica is one of the aetiological trematodes associated with fascioliasis, which heavily impacts food-production systems and human and animal welfare on a global scale. In the absence of a vaccine, fascioliasis control and treatment is restricted to pasture management, such as clean grazing, and a limited array of chemotherapies, to which signs of resistance are beginning to appear. Research into novel control strategies is therefore urgently required and the advent of ‘omics technologies presents considerable opportunity for novel drug and vaccine target discovery. Here, interrogation of the first available F. gigantica newly excysted juvenile (NEJ) transcriptome revealed several protein families of current interest to parasitic flatworm vaccine research, including orthologues of mammalian complement regulator CD59 of the Ly6 family. Ly6 proteins have previously been identified on the tegument of Schistosoma mansoni and induced protective immunity in vaccination trials. Incorporating the recently available F. gigantica genome, the current work revealed 20 novel Ly6 family members in F. gigantica and, in parallel, significantly extended the F. hepatica complement from 3 to 18 members. Phylogenetic analysis revealed several distinct clades within the family, some of which are unique to Fasciola spp. trematodes. Analysis of available proteomic databases also revealed three of the newly discovered FhLy6s were present in extracellular vesicles, which have previously been prioritised in studying the host-parasite interface. The presentation of this new transcriptomic resource, in addition to the Ly6 family proteins here identified, represents a wealth of opportunity for future vaccine research.

Incorporating the recently available F. gigantica genome, the current work revealed 20 novel Ly6 family members in F. gigantica and, in parallel, significantly extended the F. hepatica complement from 3 to 18 members.

Identification of Myoferlin, a Potential Serodiagnostic Antigen of Clonorchiasis, via Immunoproteomic Analysis of Sera From Different Infection Periods and Excretory-Secretory Products of Clonorchis sinensis

Clonorchiasis, which is caused by Clonorchis sinensis, is an important foodborne disease worldwide. The excretory-secretory products (ESPs) of C. sinensis play important roles in host-parasite interactions by acting as causative agents. In the present study, the ESPs and sera positive for C. sinensis were collected to identify proteins specific to the sera of C. sinensis (i.e., proteins that do not cross-react with Fasciola hepatica and Schistosoma japonicum) at different infection periods. Briefly, white Japanese rabbits were artificially infected with C. sinensis, and their sera were collected at 7 days post-infection (dpi), 14 dpi, 35 dpi, and 77 dpi. To identify the specific proteins in C. sinensis, a co-immunoprecipitation (Co-IP) assay was conducted using shotgun liquid chromatography tandem-mass spectrometry (LC-MS/MS) to pull down the sera roots of C. sinensis, F. hepatica, and S. japonicum. For the annotated proteins, 32, 18, 39, and 35 proteins specific to C. sinensis were pulled down by the infected sera at 7, 14, 35, and 77 dpi, respectively. Three proteins, Dynein light chain-1, Dynein light chain-2 and Myoferlin were detected in all infection periods. Of these proteins, myoferlin is known to be overexpressed in several human cancers and could be a promising biomarker and therapeutic target for cancer cases. Accordingly, this protein was selected for further studies. To achieve a better expression, myoferlin was truncated into two parts, Myof1 and Myof2 (1,500 bp and 810 bp), based on the antigenic epitopes provided by bioinformatics. The estimated molecular weight of the recombinant proteins was 57.3 ku (Myof1) and 31.3 ku (Myof2). Further, both Myof1 and Myof2 could be probed by the sera from rabbits infected with C. sinensis. No cross-reaction occurred with the positive sera of S. japonica, F. hepatica, and negative controls. Such findings indicate that myoferlin may be an important diagnostic antigen present in the ESPs. Overall, the present study provides new insights into proteomic changes between ESPs and hosts in different infection periods by LC-MS/MS. Moreover, myoferlin, as a biomarker, may be used to develop an objective method for future diagnosis of clonorchiasis.

Pathogenicity and virulence of the liver flukes Fasciola hepatica and Fasciola Gigantica that cause the zoonosis Fasciolosis

Fasciolosis caused by the liver flukes Fasciola hepatica and Fasciola gigantica is one of the most important neglected parasitic diseases of humans and animals. The ability of the parasites to infect and multiply in their intermediate snail hosts, and their adaptation to a wide variety of mammalian definitive hosts contribute to their high transmissibility and distribution. Within the mammalian host, the trauma caused by the immature flukes burrowing through the liver parenchyma is associated with most of the pathogenesis. Similarly, the feeding activity and the physical presence of large flukes in the bile ducts can lead to anemia, inflammation, obstruction and cholangitis. The high frequency of non-synonymous polymorphisms found in Fasciola spp. genes allows for adaptation and invasion of a broad range of hosts. This is also facilitated by parasite’s excretory-secretory (ES) molecules that mediate physiological changes that allows their establishment within the host. ES contains cathepsin peptidases that aid parasite invasion by degrading collagen and fibronectin. In the bile ducts, cathepsin-L is critical to hemoglobin digestion during feeding activities. Other molecules (peroxiredoxin, cathepsin-L and Kunitz-type inhibitor) stimulate a strong immune response polarized toward a Treg/Th2 phenotype that favors fluke’s survival. Helminth defense molecule, fatty acid binding proteins, Fasciola-specific glycans and miRNAs modulate host pro-inflammatory responses, while antioxidant scavenger enzymes work in an orchestrated way to deter host oxidant-mediated damage. Combining these strategies Fasciola spp. survive for decades within their mammalian host, where they reproduce and spread to become one of the most widespread zoonotic worm parasites in the world.

Proteomic Analysis of Fasciola hepatica Excretory and Secretory Products Co-Immunoprecipitated Using Time Course Infection Sera

Fasciola hepatica is a widespread pathogen that is known for its harmful effects on the health and productivity of ruminant animals. To identify the proteins present in all periods of infection with F. hepatica but not in those with Fasciola gigantica by shotgun liquid chromatography–tandem mass spectrometry (LC–MS/MS), we collected the ESPs and sera of F. hepatica and F. gigantica. In this study, the sheep were artificially infected with F. hepatica and the sera were collected at five different periods: 3 days post-infection (dpi), 7 dpi, 21 dpi, 63 dpi, and 112 dpi. The interacting proteins were pulled down from the sheep sera of all five periods and the sera with F. gigantica by co-immunoprecipitation (Co-IP) assay, before being identified by LC–MS/MS analysis. Thirty, twenty-two, twenty-three, twenty-seven, and twenty-two proteins were pulled down by the infected sera at 3 dpi, 7 dpi, 21 dpi, 63 dpi, and 112 dpi, respectively. Among them, 12 proteins existed in all periods, while six proteins could be detected in all periods in F. hepatica but not in F. gigantica. Protein relative pathway analysis revealed that these proteins mainly refer to the metabolism, regulation of genetic activity, and signal transduction of F. hepatica. In conclusion, this study provides meaningful data for the diagnosis of fasciolosis and to understand the interactions between F. hepatica and the host.

Fasciola gigantica tegumental calcium-binding EF-hand protein 4 exerts immunomodulatory effects on goat monocytes

Background

The liver fluke Fasciola gigantica secretes excretory-secretory proteins during infection to mediate its interaction with the host. In this study, we investigated the immunomodulatory effects of a recombinant tegumental calcium-binding EF-hand protein 4 of F. gigantica (rFg-CaBP4) on goat monocytes.

Methods

The rFg-CaBP4 protein was induced and purified by affinity chromatography. The immunogenic reaction of rFg-CaBP4 against specific antibodies was detected through western blot analysis. The binding of rFg-CaBP4 on surface of goat monocytes was visualized by immunofluorescence assay. The localization of CaBP4 within adult fluke structure was detected by immunohistochemical analysis. The cytokine transcription levels in response to rFg-CaBP4 were examined using ABI 7500 real-time PCR system. The expression of the major histocompatibility complex (MHC) class-II molecule (MHC-II) in response to rFg-CaBP4 protein was analyzed using Flow cytometry.

Results

The isopropyl-ß-D-thiogalactopyranoside-induced rFg-CaBP4 protein reacted with rat sera containing anti-rFg-CaBP4 polyclonal antibodies in a western blot analysis. The adhesion of rFg-CaBP4 to monocytes was visualized by immunofluorescence and laser scanning confocal microscopy. Immunohistochemical analysis localized native CaBP4 to the oral sucker, pharynx, genital pore, acetabulum and tegument of adult F. gigantica. Co-incubation of rFg-CaBP4 with concanavalin A-stimulated monocytes increased the transcription levels of interleukin (IL)-2, IL-4, interferon gamma and transforming growth factor-β. However, a reduction in the expression of IL-10 and no change in the expression of tumor necrosis factor-α were detected. Additionally, rFg-CaBP4-treated monocytes exhibited a marked increase in the expression of the major histocompatibility complex (MHC) class-II molecule (MHC-II) and a decrease in MHC-I expression, in a dose-dependent manner.

Conclusions

These findings provide additional evidence that calcium-binding EF-hand proteins play roles in host-parasite interaction. Further characterization of the immunomodulatory role of rFg-CaBP4 should expand our understanding of the strategies used by F. gigantica to evade the host immune responses.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04784-5.

Fasciola gigantica-Derived Excretory-Secretory Products Alter the Expression of mRNAs, miRNAs, lncRNAs, and circRNAs Involved in the Immune Response and Metabolism in Goat Peripheral Blood Mononuclear Cells

Fasciola gigantica produces excretory-secretory products (ESPs) with immune-modulating effects to promote its own survival. In this study, we performed RNA-seq to gain a comprehensive global understanding of changes in the expression of mRNAs, miRNAs, lncRNAs, and circRNAs in goat peripheral blood mononuclear cells (PBMCs) treated with F. gigantica ESPs. A total of 1,544 differently expressed mRNAs (790 upregulated and 754 downregulated genes), 30 differently expressed miRNAs (24 upregulated and 6 downregulated genes), 136 differently expressed circRNAs (83 upregulated and 53 downregulated genes), and 1,194 differently expressed lncRNAs (215 upregulated and 979 downregulated genes) were identified. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses revealed that F. gigantica ESPs altered the expression of genes associated with the host immune response, receptor signaling, disease and metabolism. Results from RNA-seq were validated by qRT-PCR. These findings provide an important resource for future investigation of the role of mRNAs and non-coding RNAs in mediating the immune-modulating effects of F. gigantica ESPs.

Trematode Proteomics: Recent Advances and Future Directions

Trematodes cause disease in millions of people worldwide, but the absence of commercial vaccines has led to an over-reliance on a handful of monotherapies to control infections. Since drug-resistant fluke populations are emerging, a deeper understanding of parasite biology and host interactions is required to identify new drug targets and immunogenic vaccine candidates. Mass spectrometry-based proteomics represents a key tool to that end. Recent studies have capitalised on the wider availability of annotated helminth genomes to achieve greater coverage of trematode proteomes and discover new aspects of the host-parasite relationship. This review focusses on these latest advances. These include how the protein components of fluke extracellular vesicles have given insight into their biogenesis and cellular interactions. In addition, how the integration of transcriptome/proteome datasets has revealed that the expression and secretion of selected families of liver fluke virulence factors and immunomodulators are regulated in accordance with parasite development and migration within the mammalian host. Furthermore, we discuss the use of immunoproteomics as a tool to identify vaccine candidates associated with protective antibody responses. Finally, we highlight how established and emerging technologies, such as laser microdissection and single-cell proteomics, could be exploited to resolve the protein profiles of discrete trematode tissues or cell types which, in combination with functional tools, could pinpoint optimal targets for fluke control.

Dysregulation of hepatic microRNA expression in C57BL/6 mice affected by excretory-secretory products of Fasciola gigantica

The excretory-secretory products released by the liver fluke Fasciola gigantica (FgESPs) play important roles in regulating the host immune response during the infection. Identification of hepatic miRNAs altered by FgESPs may improve our understanding of the pathogenesis of F. gigantica infection. In this study, we investigated the alterations in the hepatic microRNAs (miRNAs) in mice treated with FgESPs using high-throughput small RNA (sRNA) sequencing and bioinformatics analysis. The expression of seven miRNAs was confirmed by quantitative stem-loop reverse transcription quantitative PCR (qRT-PCR). A total of 1,313 miRNAs were identified in the liver of mice, and the differentially expressed (DE) miRNAs varied across the time lapsed post exposure to FgESPs. We identified 67, 154 and 53 dysregulated miRNAs at 1, 4 and 12 weeks post-exposure, respectively. 5 miRNAs (miR-126a-3p, miR-150-5p, miR-155-5p, miR-181a-5p and miR-362-3p) were commonly dysregulated at the three time points. We also found that most of the DE miRNAs were induced by FgESPs in the mouse liver after 4 weeks of exposure. These were subjected to Gene Ontology (GO) enrichment analysis, which showed that the predicted targets of the hepatic DE miRNAs of mice 4 weeks of FgESPs injection were enriched in GO terms, including cell membrane, ion binding, cellular communication, organelle and DNA damage. KEGG analysis indicated that the predicted targets of the most downregulated miRNAs were involved in 15 neural activity-related pathways, 6 digestion-related pathways, 20 immune response-related pathways and 17 cancer-related pathways. These data provide new insights into how FgESPs can dysregulate hepatic miRNAs, which play important roles in modulating several aspects of F. gigantica pathogenesis.